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Discussion Starter #1
Hi guys,

well last week I started car, and after 30 second, car change tone like it is running on 4 or 5 cylinders . After one minute car "repair" itself, and ran fine.
Yesterday I started car again, and it started nice, but again after 15-20seconds it change sound again, and it was heard like Subaru....and did not repair itself....
Well I unplug spark wires from coil, and found that on 3 and 6 cylinder there is no spark (first coil from front to rear ).

I had this same problem 7 years back, and change and tested PTU, Coils, wires, and finally I also send my ECU to AvPro for repair, and of course it was ECU. Car ran fine up to now. (car is 92 TT).
Now is it possible that is ECU again, or is PTU or Coil.... From my reading this forum I found some threads for not working 3 and 6 cylinder and always was ECU. Or am I wrong?

I just wanna get my car working again, before I do:
  • DR 750 swap
  • hotwire ignition coils
  • Spark plug cold 8
  • ARC 2+safc2 combo
  • Alu 2 piece drive shaft
  • Alcohol water injection
  • and tune again
 

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Well you will have to check all the wiring, from ECU to PTU signal, you can remove the CAS and rotate it by hand, with ignition ON and you should hear and see the injectors firing and spark plugs you can disconnect the injector plug so no fuel is spraying and diagnose the PTU/coilpack, I once used a set of LEDS connected to the 3v outputs from the ecu to PTU, that way I found that my ecu was sending the correct signal, it was a wiring problem with the coilpack.
 

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Hi guys,

well last week I started car, and after 30 second, car change tone like it is running on 4 or 5 cylinders . After one minute car "repair" itself, and ran fine.
Yesterday I started car again, and it started nice, but again after 15-20seconds it change sound again, and it was heard like Subaru....and did not repair itself....
Well I unplug spark wires from coil, and found that on 3 and 6 cylinder there is no spark (first coil from front to rear ).

I had this same problem 7 years back, and change and tested PTU, Coils, wires, and finally I also send my ECU to AvPro for repair, and of course it was ECU. Car ran fine up to now. (car is 92 TT).
Now is it possible that is ECU again, or is PTU or Coil.... From my reading this forum I found some threads for not working 3 and 6 cylinder and always was ECU. Or am I wrong?
You described the exact symptoms of a failing PTU. This exact same thing happened to me when my PTU started going out; it would intermittently stop sending the signal to one of the coil packs, which means you lose spark on 2 cylinders. Note, your tach should also read 4/6 of what the actual RPM is when this happens. I also got a CEL, which would disappear when the PTU "fixed itself".

Of course it could also be a coil or the ECU, but the intermittent nature and problem you described sound like PTU, so that should be the first check. You can easily remove and bench test the PTU, but make sure you do so when it is not working (if you test it after it has "fixed itself" it may bench test fine)
 

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Discussion Starter #4
I will bench test PTU to se what I get. Will post back... Should I heat it with fan a little bit, because I read somewhere, that when sensors are cold the give you one readings, but if you heat them, like when engine is running, you can get different numbers?
 

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If you don't find anything wrong with PTU, check the wiring harness between the PTU and the coil pack there's a yellow wire that splices into the 3-6 coil line, and a portion of it hangs out of the wiring loom.

Spent 9 months chasing an ignition issue like yours just to find out that wire had lost some insulation there and was shorting to the trans.

Sent from my SM-G892A using Tapatalk
 

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Discussion Starter #7
Ok guys,

Today I had finally some time for my Stealth.

I pulled Coils out and measure their resistance.
Primary Coil resistence (measure on connector)
Coil A (1-4 cylinder)= 0,8 Ohm
Coil B (2-5 cylinder)= 1,9 Ohm
Coil C (3-6 cylinder)= 1,9 Ohm


Secondary Coil resistence (measure between each coil on the top where cable connect)
My value is all three were12,7kOhm
Standard value is 11,3-15,3kOhm

I measure also my old Coils and had same results.

Well in the book it they say that standard value = 0,67-0,81 ohm.

So what do you guys think?

I need to measure also PTU but just dont know what to do with my multimeter (I have OHM, V and A on my multimeter), and dont know what should I use for measure continuity?) Help is apreciated :)
 

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Discussion Starter #9
Nope, because I know only one friend who has 93 TT but his car is apart, spun bearing.... I just really hope that my Ecu is ok, because it was already repair by AvPro years back
 

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Discussion Starter #10
Ok guys, I measure also PTU.

1-4 coil have 1,77mA and 43kOhm ( with 1,5V battery)
2-5 coil have 1,77mA and 43kOhm ( with 1,5V battery)
3-6 coil have 1,77mA and 43kOhm ( with 1,5V battery)

or should I check / measure anything else?

Is my PTU ok?
 

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Discussion Starter #11
IAs I mentionted in the first post, my car starts nice, but after few minutes, car start to run withou 3-6 coil. Of course there is heat under the hood.
Now I remebered this, and measure again with hairdrier on ptu. So after 2 minutes of heating this are results....

1-4 coil have 1,60mA and 43kOhm ( with 1,5V battery)
2-5 coil have 1,59mA and 43kOhm ( with 1,5V battery)
3-6 coil have 1,58mA and 43kOhm ( with 1,5V battery)

Any clue if this is normal or not?
 

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Discussion Starter #13
If you don't find anything wrong with PTU, check the wiring harness between the PTU and the coil pack there's a yellow wire that splices into the 3-6 coil line, and a portion of it hangs out of the wiring loom.

Spent 9 months chasing an ignition issue like yours just to find out that wire had lost some insulation there and was shorting to the trans

Sent from my SM-G892A using Tapatalk
Which yellow wire you mean? We have 3 connectors, 1 goes to coil (4 pin), then two connectors to PTU. Big and small connector(3pin).
I dont have any yellow wire there, just one with yellow stripe
 

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Which yellow wire you mean? We have 3 connectors, 1 goes to coil (4 pin), then two connectors to PTU. Big and small connector(3pin).
I dont have any yellow wire there, just one with yellow stripe
The 4 pin. It's kinda far down in the harness tho. You'll have to remove a few things to get to where it hangs out. Easy way to tell if that portion is stripped is just to check if the incoming line to the front most coil is shorted to ground

Sent from my SM-G892A using Tapatalk
 

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IAs I mentionted in the first post, my car starts nice, but after few minutes, car start to run withou 3-6 coil. Of course there is heat under the hood.
Now I remebered this, and measure again with hairdrier on ptu. So after 2 minutes of heating this are results....

1-4 coil have 1,60mA and 43kOhm ( with 1,5V battery)
2-5 coil have 1,59mA and 43kOhm ( with 1,5V battery)
3-6 coil have 1,58mA and 43kOhm ( with 1,5V battery)

Any clue if this is normal or not?
When you pulled the PTU to do the bench test, did you have a check engine light on? The PTU problem can be intermittent; you need to test it when the problem is occuring. It could bench test fine, then run fine for a bit, only to randomly drop a coil again later on. In my case, i drove the car until the CEL came back and i lost spark on one coil, pulled the PTU, and it bench tested bad on that coil.
 

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Discussion Starter #16
No because, I start doing on the car, while the cel was on, but I had to stop in the mean time because I had to do some other thing. So next mornig I start checking PTU.....
But I will order new PTU, because it is original on the car, that has never been changed. And I will report back.

Will check for wires too.
After that I will need to pull ECU, if that wont work.
 
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